In Japanese Unexamined Patent Application Publication No. 2008-152438, awake levels, determined from the degree of monotonicity of how monotonous the driver's operation of operating pedals or shifting gears is or from the frequency of occurrence of erratic driving behaviors of a vehicle resulting from unstable steering, are sequentially stored and displayed as a time-series bar chart. When the current awake level is lower than a certain level, the apparatus alerts the driver via a sound indicator or the like.
In the technology described in Japanese Unexamined Patent Application Publication No. 2008-152438, information regarding the awake level of a driver is displayed as a bar chart. Thus, for a low awake level of which the driver needs to be alerted, no graph such as bar chart is displayed. It is therefore difficult to accurately inform the driver of the tendency of his/her driving state until a sound-based alert or the like has been issued.
That is, it is difficult to accurately inform a driver of information regarding driving stability.